JPH0478743B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a laminated nonwoven fabric sheet that can be suitably used for durable microfilters.

[Prior art] Conventionally, microfilters have usually been made of ultrafine glass fibers bonded together with a binder, but microfilters made of ultrafine glass fibers are not strong enough to be easily damaged during bending or installation. They also have the disadvantage that they are easily damaged by vibration during use, making them unable to function as a filter.

On the other hand, in view of the disadvantages of using ultra-fine glass fibers, it is possible to use ultra-fine fiber sheets other than glass fibers.

Melt blowing is known as one method for obtaining ultrafine fiber sheets with an average fineness of 0.8d or less, but the sheets obtained by this melt blowing method have low tensile strength because they are made of undrawn fibers. There was a problem that it was weak and could only be obtained with a weight of about 0.5 kg/5 cm, so it could not be used for filter purposes.

On the other hand, in order to improve the dimensional stability of sheets obtained by melt blowing, methods are known in which other fiber materials are laminated and needle punching or water punching is performed. Since holes are formed that penetrate in the thickness direction, even if this was attempted to be applied to a filter, dust would leak, resulting in a drawback that it could not be used in a filter.

Furthermore, it is conceivable to join the two with an adhesive instead of the needle punching or water punching method, but there is a problem that pressure loss tends to increase because the adhesive obstructs air circulation.

[Problems to be Solved by the Invention] The present invention was devised in view of the various drawbacks of the prior art, and aims to provide high collection performance with a small increase in pressure loss and durability. The purpose of the present invention is to provide a method for producing a laminated nonwoven fabric sheet suitable for use in an excellent microfilter.

[Means to solve the problem] Made of stretched synthetic fiber and has a basis weight of 20g/
^A synthetic fiber non-woven fabric having an air flow rate of 70 g/m ² or more and an air permeability of 20 c.c./cm ² /sec or more is placed on a melt-blown fiber collection conveyor, and on top of the synthetic fiber non-woven fabric,
The distance between the melt blowing nozzle and the collection conveyor is 5 cm to 60 cm, and the melt-blown fibers are injected, collected, and bonded at a basis weight larger than the basis weight of the synthetic fiber nonwoven fabric made of the stretched synthetic fibers. This is achieved by a method for manufacturing a laminated nonwoven fabric sheet for a microfilter, which comprises manufacturing a laminated nonwoven fabric sheet by stacking the sheets.

[Function] The present invention will be explained in more detail below.

The method for producing a laminated nonwoven fabric sheet for a microfilter of the present invention includes placing a synthetic fiber nonwoven fabric made of stretched synthetic fibers on a conveyor for collecting meltblown fibers, and placing a melt blowing nozzle and a collecting cap on the synthetic fiber nonwoven fabric. The distance from the collection conveyor is 5~
According to the present invention, melt-blown fibers of 60 cm are directly injected and bonded to the nonwoven fabric in a layered manner.According to the present invention, ultrafine fibers with an average fineness of 0.8 d or less are applied to the nonwoven fabric made of drawn synthetic fibers. A microfilter in which undrawn fibers are fused to each other and successively laminated in a scale-like manner while maintaining a surface temperature that allows for fusion, reducing the passage of ultrafine dust and dramatically increasing collection efficiency. This makes it possible to produce a nonwoven fabric sheet that is optimal for various purposes.

In addition, since the melt-blown sheet is reinforced with a non-woven fabric made of stretched synthetic fibers, when used as a filter, there is no breakage and its durability can be greatly improved. This is because the bonding between the two is carried out by utilizing the self-fusing properties and anchoring effect of the melt-blown sheet, so the use of binders, etc. can be completely eliminated, or even if they are used, only a very small amount is used. This has the advantage that a very high-performance microfilter with a slow increase in pressure loss can be obtained.

In the present invention, the nonwoven fabric made of the drawn synthetic fiber has a basis weight of 20 g/m ² or more and 70 g/m ²
It is important to use materials within the following range; if the basis weight is less than 20g/ ^m2 , it is generally difficult to obtain a large reinforcing effect, and if it is greater than 70g/ ^m2 , the overall Problems such as an increase in the basis weight and an increase in pressure loss are undesirable.

The nonwoven fabric made of drawn synthetic fibers is mainly used for reinforcement purposes, and is a melt-blown fabric made of ultrafine undrawn fibers with an average fineness of 0.8 d or less that exhibits the main filter performance for microfilters. It is important to use a material with a lower basis weight than a non-woven fabric sheet.

In the present invention, the melt-blown fiber is a finite-length fiber made of discontinuous filaments made of a fiber-forming organic polymer such as polyamide, polyester, polyolefin, or a copolymer thereof, and is not drawn. It is composed of fiber threads, and each of the undrawn fiber threads is bonded and deposited on a nonwoven fabric made of synthetic fibers that are fully spread and drawn without bunching, that is, without bunching. A thin melt-blown sheet is formed, and these sheets are overlapped in the form of scales to form a laminated non-woven fiber sheet, and the points of contact between each component fiber and the points of contact between the melt-blown sheet and the stretched synthetic fiber non-woven fabric are teeth,
It is formed by fusing the constituent fibers themselves.

In order to obtain such a laminated nonwoven fabric sheet, which is the intended purpose of the present invention, the melt blowing conditions, particularly the temperature of the melt blowing fibers joined to the stretched nonwoven fabric, and the temperature of the melt blowing die and collection conveyor must be adjusted. It is very important to set the distance appropriately, and the collection distance should be 5cm to 60cm.
It is important that the distance be within the range of 20cm to 60cm, preferably 20cm to 60cm. Furthermore, the surface temperature of the melt-blown fibers being collected is determined by the Tg of the fibers.
When the temperature is higher than the glass transition temperature, a laminated nonwoven sheet with high peel strength and sufficient air permeability can be easily obtained.

If the collection distance is below the above range and the fiber surface temperature is extremely high, the melt blown sheet will turn into a film and cannot be used as a filter, which is undesirable. Since the temperature drop is large, the bonding strength cannot be sufficiently increased, resulting in a filter that is easily damaged.

Further, in the present invention, in order to increase the bonding force due to the anchor effect, it is important to use a stretched synthetic fiber nonwoven fabric for bonding that has an air permeability of 20 c.c./cm ² /sec or more. In addition, in order to obtain both the bonding effect and the reinforcing effect sufficiently and appropriately, the basis weight should be 20g/m ² or more and 70g/m ² as described above.
It is important to use the following range.

Furthermore, in order to further increase the bonding strength of the laminated nonwoven sheet of the present invention, it is preferable to heat the stretched nonwoven fabric made of synthetic fibers in advance and then bond them to the meltblown fibers.

As the nonwoven fabric made of drawn synthetic fibers used in the method of the present invention, known short fiber nonwoven fabrics, needle punched nonwoven fabrics, spunbond nonwoven fabrics, etc. can be used as appropriate. The fiber material for the nonwoven fabric used for reinforcement is organic polymers (polyester, polyamide, etc.) due to their strength and durability.
Polyolefin, acrylic, etc.) are used. According to the various findings of the present inventors, stretched polyester fibers are preferably used as the fiber material in order to obtain a higher and better reinforcing effect. In particular, polyester spunbond nonwoven fabrics made of filaments are highly preferred as reinforcing nonwoven fabrics because they have good air permeability and high strength.

When manufacturing a laminated nonwoven sheet for a microfilter by the method of the present invention, the laminated nonwoven sheet has a concentration of 1 to 200% in terms of collection efficiency and pressure loss.
It is preferable to have an air permeability of cc/cm ² /sec. If the air permeability of the laminated nonwoven sheet is less than 1 c.c./cm ² /s, the pressure loss will become too large, which is undesirable, and if it is more than 200 c.c./cm ² /s, it will not be possible to trap dust. This is not preferable because the collection efficiency decreases.

Further, the tensile strength of the laminated nonwoven sheet is preferably 1 kg/5 cm or more from the viewpoint of practical performance as a filter.

Next, the present invention will be further explained based on the drawings and the like.

FIG. 1 is a perspective view schematically showing the structure of an example of a nonwoven fabric for microfilters obtained by the manufacturing method of the present invention. A melt-blown sheet made of drawn fibers, 3 a nonwoven fabric made of drawn synthetic fibers, and 4 a joint.

FIG. 2 is an enlarged perspective view schematically showing the structure of the melt-blown sheet 2 used in the manufacturing method of the present invention, in which 5 is an ultra-fine fiber with an average fineness of 0.8d or less, and 6 is an ultra-fine fiber of each ultra-fine fiber. The fused portion 7 indicates a scale-like unit sheet.

FIG. 3 is a schematic diagram illustrating an example of an embodiment of the method for producing a laminated nonwoven fabric sheet of the present invention;
is the spinneret, 9 is the melt-blown fiber, 10
is a nonwoven fabric made of drawn synthetic fibers, and the fibers 9 melt-blown from the spinneret 8 are nonwoven fabrics 10.
The melt-blown fibers are directly injected onto the fibers and bonded directly by the fusion effect and anchor effect of the melt-blown fibers. 1
1 is a breathable conveyor, and 12 is a suction.

As shown in FIG. 3, the method of the present invention is made of stretched synthetic fibers, has a basis weight of 20 g/m ² or more and 70 g/m ² or less, and has an air permeability of 20 c.c./cm ² /sec or more. A synthetic fiber non-woven fabric 10 was placed on a melt-blown fiber collection conveyor 11, and melt-blown was carried out on the synthetic fiber non-woven fabric 10 with the distance between the melt-blowing spinneret 8 and the collection conveyor 11 being 5 to 60 cm. The fibers 9 are injected and collected to obtain a laminated nonwoven fabric sheet 1 having a structure as shown in FIG.

[Effects] According to the method of the present invention, as described above, it is possible to obtain a very high-performance microfilter that has sufficient durability and slows down the increase in pressure loss.

This is also a relatively simple and rational manufacturing process, and the high-performance microfilter can be obtained very simply and at low cost.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples. In the following explanation, the amount of ventilation, peel strength, and thickness were measured by the following method.

Air flow rate: Measured according to JIS L-1096A (Fragir method).

Peel strength of joint surface: Measured according to JIS K-6328.

Thickness: Measured according to JIS L-1096 (diamond cage method).

Example 1 In the process mode shown in FIG. 3, polyester spunbond nonwoven fabric (fineness 5d, basis weight 20g/m ² , air permeability 640
cc/cm ² /sec), the melt-blown fibers 9 made of polypropylene were directly injected onto the nonwoven fabric to form a layered structure and then bonded together to form a laminated nonwoven fabric sheet 1.

Melt blowing conditions are: spinning temperature 340℃, injection air temperature 340℃, discharge rate 8g/min/hole, injection air flow rate 80N/min/hole, collection distance 35cm.
and the average fineness is 0.5d. Further, the surface temperature of the melt-blown fibers immediately before joining with the drawn fiber nonwoven fabric was measured with a thermal imager and found to be 110°C.

The fabric weight of the laminated nonwoven sheet obtained in this way is 350
g/m ² , air flow rate 62c.c./cm ² /sec, tensile strength 5 vertically
Kg/5cm, width 3Kg/5cm. Moreover, the peel strength of the bonded surface was 300 g/2 cm.

When the laminated nonwoven fabric sheet obtained in this way was used as a microfilter, it was a high-performance filter capable of collecting dust of 0.3 μ or more with a collection efficiency of 99.9% without damage at a wind speed of 1 m/min. .

Example 2 Melt-blown fibers made of polybutylene terephthalate were directly injected onto a short fiber nonwoven fabric made of polyester fibers drawn in the same process as in Example 1 to produce a laminated nonwoven fabric sheet 1.

Melt blowing conditions are spinning temperature 294℃, discharge amount
15g/min/hole, injection air temperature 305℃, injection air amount 100N/min/hole, collection distance 25cm
It was hot. Average fineness of meltblown fibers
0.2d, the sheet apparent density was 0.35g/cm ³ , and the fiber surface temperature immediately before joining was 123°C.

The short fiber nonwoven fabric made of stretched polyester fibers is made by bonding polyester short fibers with a fineness of 3D with an acrylic binder, and has a basis weight of 40g/
m ² and the airflow rate is 600 c.c./cm ² /sec.

The laminated nonwoven sheet thus obtained has a basis weight of
The weight was 260 g/m ² , the airflow rate was 83 c.c./cm ² /sec, and the tensile strength was 6 kg/5 cm vertically and 1.2 kg/5 cm horizontally.

When such a laminated nonwoven sheet was used as a filter for a vacuum cleaner at a wind speed of 10 m/min, it was a high-performance sheet that could collect dust of 1μ or more with a collection efficiency of 99.9% or more without any damage. It was hot.

Example 3 A laminated nonwoven sheet was manufactured by directly spraying melt-blown fibers made of nylon 6 onto a needle-punched nonwoven fabric made of drawn polyester fibers that had been preheated to 100°C.

Melt blowing conditions are spinning temperature 290℃,
Discharge rate 15g/min/hole, injection air temperature 290℃,
Injection air amount 100N/min/hole, collection distance is
40cm, the fiber surface temperature immediately before joining is 100℃,
The average fineness of the fibers was 0.3d.

The nonwoven fabric made of polyester drawn fibers has a basis weight of 70 g/m ² , an air permeability of 380 c.c./cm ² /sec, and a fineness of 5 d.

The laminated nonwoven fabric sheet thus obtained has a basis weight of
410g/m ² , airflow rate 52c.c./cm ² /sec, tensile strength vertical
The peel strength of the joint surface was 24 kg/5 cm, 12 kg/5 cm horizontally, and 500 g/2 cm.

When this laminated nonwoven fabric sheet was used as a liquid filter, it could be used with high collection efficiency without breakage.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing an example structure of a laminated nonwoven fabric sheet for a microfilter obtained by the manufacturing method of the present invention. FIG. 2 is an enlarged perspective view schematically showing the structure of a melt blown sheet used in the manufacturing method of the present invention. FIG. 3 is a schematic model diagram illustrating an example of an embodiment of the method for manufacturing a laminated nonwoven sheet of the present invention. 1: Laminated non-woven fabric sheet, 2, 9: Melt-blown sheet, 3, 10: Non-woven fabric made of stretched synthetic fibers, 4: Joint, 8: Melt-blowing spinneret, 11: Conveyor, 12: Suction.

Claims (1)

[Claims] 1. Made of stretched synthetic fiber and has a basis weight of 20
g/m ² or more and 70 g/m ² or less, ventilation rate 20 c.c./cm ² /
A synthetic fiber nonwoven fabric having a length of at least 2 seconds is placed on a conveyor for collecting melt-blown fibers, and the distance between the melt-blowing nozzle and the collecting conveyor is set to 5 cm to 60 cm, and the stretched A method for producing a laminated nonwoven fabric sheet for a microfilter, characterized in that the laminated nonwoven fabric sheet is produced by jetting, collecting, and bonding and depositing melt-blown fibers with a basis weight larger than that of a synthetic fiber nonwoven fabric made of synthetic fibers. 2. The method for producing a laminated nonwoven fabric sheet for microfilters according to claim 1, wherein the drawn synthetic fibers are polyester fibers.